Hydrocephalus is a condition afflicting patients who are unable to regulate cerebrospinal fluid flow through their body's own natural pathways. Produced by the ventricular system, cerebrospinal fluid (CSF) is normally absorbed by the body's venous system. In a patient suffering from hydrocephalus, the cerebrospinal fluid is not absorbed in this manner, but instead accumulates in the ventricles of the patient's brain. If left untreated, the increasing volume of fluid elevates the patient's intracranial pressure and can lead to serious medical conditions such as compression of the brain tissue and impaired blood flow to the brain.
The treatment of hydrocephalus has conventionally involved draining the excess fluid away from the ventricles and rerouting the cerebrospinal fluid to another area of the patient's body, such as the abdomen or vascular system. A drainage system, commonly referred to as a shunt, is often used to carry out the transfer of fluid. In order to install the shunt, typically a scalp incision is made and a small hole is drilled in the skull. A proximal, or ventricular, catheter is installed in the ventricular cavity of the patient's brain, while a distal, or drainage, catheter is installed in that portion of the patient's body where the excess fluid is to be reintroduced.
To regulate the flow of cerebrospinal fluid and maintain the proper pressure in the ventricles, a pump or one-way control valve can be placed between the proximal and distal catheters. Generally, the shunt systems include a valve mechanism that operates to permit fluid flow only once the fluid pressure reaches a certain threshold level. That is, fluid enters the valve only when the fluid pressure overcomes the valve mechanism's resistance to open. Some valve mechanisms permit the adjustment, or programming, of the opening pressure level, or resistance level, at which fluid flow commences. These valve mechanisms can comprise a variety of configurations. For example, the valve mechanism can be configured as a ball-in-cone as illustrated and described in U.S. Pat. Nos. 3,886,948, 4,332,255, 4,387,715, 4,551,128, 4,595,390, 4,615,691, 4,772,257, and 5,928,182, all of which are hereby incorporated by reference.
Research has shown that it may be possible to successfully remove a shunt in younger hydrocephalus patients by limiting the shunt-dependent flow of the cerebrospinal fluid. In particular, the operating pressure of a programmable valve can be gradually increased to activate regular circulation of cerebrospinal fluid. As a result of careful control of the valve pressure, once sufficient cerebral development has been achieved and the patient's intracranial pressure has been normalized, the shunt can be successfully removed. Current valves, however, do not allow the threshold pressure to be adjusted in small increments and up to a threshold pressure at which the patient's own circulation system is substantially responsible for circulating cerebrospinal fluid, i.e., a threshold pressure at which shunt independence can be achieved.
Accordingly, there is a need for a valve device that can be used to gradually increase the threshold pressure, preferably in relatively small and precise increments, thereby forcing the patient's own physiologic resorption system to compensate and eventually become shunt independent.